How to get a Matte/Clay render
A simple shader node should work in Cycles render. It's using the new Principled BSDF shader with the roughness set to 1. Alternatively you could use a Diffuse BSDF shader with the roughness set to 1 and get the same result.



I have a main sun light source  with Ambient Occlusion under World->Ambient Occlusion and set the value to .1. If you increase the value for the Ambient Occlusion, you'll see less shadows.